OBJECTIVE: Skin-to-skin contact (kangarooing) is regarded as an important method to improve intensive care in premature infants. There is still demand for investigations of its impact on physiological parameters. STUDY DESIGN: We examined 53 preterm infants of < 1800 gm in a prospective, pretest-test-posttest design study during incubator care (60 minutes), skin-to-skin contact (90 minutes), and incubator care again (90 minutes). Heart rate, respiratory rate, oxygen saturation (SaO2), transcutaneous pO2 (tcpO2), transcutaneous pCO2, rectal temperature, and fraction of inspired oxygen were measured. RESULTS: The heart rate increased during skin-to-skin contact by 5 beats per minute (p < 0.001), the respiratory rate dropped by 5/minute (p < 0.01), the SaO2 improved by 0.4% (p < 0.05) accompanied by an increase of tcpO2 of 4.8 mm Hg (p < 0.001), the tcpCO2 dropped by 1.2 mm Hg (p < 0.001), and the rectal temperature increased by 0.3 degree C (p < 0.001). Analyzing three groups separately by postnatal weight, we observed the smallest increase in heart rate and the highest decrease in respiratory rate in infants of < 1000 gm (p < 0.001). The increase in SaO2 and in the tcpO2 doubles in infants of < 1000 gm compared with infants of > 1000 gm (p < 0.001). All changes were independent of postnatal age. CONCLUSION: During skin-to-skin contact, preterm infants not only remain clinically stable but also show a more efficient gas exchange. Although the patient is removed (transferred) from the incubator, there is no risk of hypothermia even in infants of < 1000 gm.